A conventional brake actuating unit and a method for monitoring the working of the brake actuating unit are disclosed, for example, by German patent application DE 10 2007 016 754 A1, which is incorporated by reference, and are used in hybrid vehicles, for example. The known brake actuating unit comprises an activation and shutoff device, which activates the pedal travel simulator in the “brake-by-wire” operating mode on decoupling of the force-transmitting connection between the brake pedal and the brake booster, and shuts it off when not in the “brake-by-wire” operating mode. In the known brake actuating unit the shutoff is necessary in order to ensure the statutory minimum deceleration in the event of a fault, that is to say at the fallback level. In this event the pedal travel simulator is disabled and the driver of the motor vehicle can obtain the braking action through the coupling of the force-transmitting connection between the brake pedal and the brake booster with the usual pedal feel.
Since the activation and shutoff device comprises parts, which are not moved in the by-wire mode, a separate check is necessary. The provision of the activation and shutoff device and the necessary method of monitoring are generally regarded as costly.